- A ten year orbit carries Egroria and its Moon between two brutal extremes:
- Two year summer
- Three year Winter
The two and a half year transition either side of summer and winter is a bad time for those not behind walls. Superpredators and scavengers, dormant during summer or winter, emerge in search of food.
Spelljammers come and go from Egroria. The skydocks sit atop the shieldwall that encompasses the only city. From here they fly to the asteroid mining colonies on the edge of the system.
The city is defended by a great stone shield wall where spelljammers dock. Miners bringing crystaline residium from the asteroid belt trade the crystal for food and water. The city must be reclaimed after the Summer years and adventurers get to clear out monsters nesting in the city.
Beyond the walls is a brutal landscape only accessible precisely when it is overrun by hostile monsters. In summer and winter they retreat into subterranean lairs.
This is a secondary city below the surface of the Moon on the side facing egroria. Used as a retreat during summer years the city has extensive tunnels where the populace farms fungi and breed lightning eels for the only edible part - their blood and intestines. Blood sausage is the singular preserved food available in the egrorian system.
Water, collected in cisterns comes from rains as the atmosphere cools or warms is vital for survival. Most Spelljammers retreat to the Asteroid belt during Summer.
The crystaline residium mined in the asteroid belt can be used in spelljammer furnaces to power flying ships. Not everyone mines for crystaline residium. Piracy and claim jumping are common.